Energy Conservation

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Revision as of 10:12, 30 May 2015 by Saucyjack (talk | contribs) (Added "Kinetic Energy Implications".)
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Implications of Constant Thrust

Doctor White has proposed that the EM Drive is capable of producing constant thrust at a constant power output. User frobnicat has shown (in the following text and image) that if this were to be true, then the EM Drive could be utilized as a source of unlimited energy. [1] This of course constitutes a violation of Conservation of Energy.

"As often remarked : for any propellantless device yielding "given constant thrust for given constant power" (ie. a definite thrust/power ratio) there is a velocity relative to a power feedback loop system above which net power surplus can be generated (indefinitely, wear apart). This velocity is simply the inverse of the thrust/power ratio : V (m/s) = power (W) / thrust (N)." -frobnicat [2]

On the assumption that the results provided by the various experimenting groups are valid, then one of the following two options as provided by user deltamass[3] and clarified by user frobnicat [4] must be true. The options are as follows:

Option 1: Energy is conserved, but there is a preferred rest frame. In essence, the drive has a maximum change in velocity (a decreasing acceleration curve) that it can impart irrespective of its starting velocity. The idea of a preferred rest frame is at odds with general relativity.

Option 2: An apparent breach of conservation of energy is possible, where the mechanism by which conservation of energy is maintained is as yet unknown. An example of a possible solution to this problem is that the drive could in some way be emitting tachyons.[5]

Tachyons are fictional particles that can travel faster than the speed of light. Sending signals faster than light, leads to violations of causality, see: Tachyonic Antitelephone.

Since option 1 leads to a violation of general relativity and option 2 leads to a violation of causality, one concludes that, with constant input power supplied to the EM Drive, the acceleration cannot be constant. As remarked by WarpTech the acceleration must decrease with increasing velocity, as per Newton's 2nd law:[6]

Acceleration = Thrust / Mass = Power / (Mass*Velocity)

So, for constant input power to the EM Drive (and constant vehicle mass), the vehicle's acceleration must decrease in inverse proportion to the vehicle's velocity. To achieve constant acceleration, increasing power must be supplied to the EM Drive, in proportion to the increasing velocity.

Kinetic Energy Implications

Given:

[math]f=ma[/math]

and

[math] e=\cfrac{1}{2}mv^2 [/math]

then

[math]a=\cfrac{f}{m}[/math]

So if this device can produce a constant force then it will produce a constant acceleration.

See Talk:Energy_Conservation for more discussion on this.

References